论文标题

使用基于混合深度学习的减少订单模型评估不稳定流量预测

Assessment of unsteady flow predictions using hybrid deep learning based reduced order models

论文作者

Bukka, Sandeep Reddy, Gupta, Rachit, Magee, Allan Ross, Jaiman, Rajeev Kumar

论文摘要

在本文中,我们提出了两个基于深度学习的混合数据驱动的减少订单模型,以预测不稳定的流体流量。第一个模型通过适当的正交分解(POD)将高保真时间序列序列数据从有限元navier-stokes stokes solver到低维子空间。 POD子空间中的时间相关系数通过复发净(闭环编码器更新)传播,并通过平均流场和POD基矢量映射到高维状态。该模型称为POD-RNN。第二个模型,称为卷积复发自动编码器网络(CRAN),使用卷积神经网络(CNN)作为具有非线性激活的线性内核层,从流场快照中提取低维特征。使用复发性(闭环方式)净进行扁平的特征,并逐渐采样(转置曲折)到高维快照。选择了两个基准问题,经过一个圆柱体并流过一个并排圆柱体的流程作为测试问题,以评估这些模型的功效。对于经过单个圆柱体的流动问题,两个模型的性能都是令人满意的,克兰有点过分。但是,它完全胜过POD-RNN模型,因为它的流动圆柱体的流动问题更复杂。由于CRAN的可伸缩性,我们简要引入了一种观察者 - 校正方法,以计算参考网格上流体 - 固定边界上的综合压力系数。该参考网格通常是结构化和均匀的网格,用于插值散射的高维场数据作为快照图像。这些输入图像在训练中很方便。这激发了我们进一步探索Cran模型在预测流体流中的应用。

In this paper, we present two deep learning-based hybrid data-driven reduced order models for the prediction of unsteady fluid flows. The first model projects the high-fidelity time series data from a finite element Navier-Stokes solver to a low-dimensional subspace via proper orthogonal decomposition (POD). The time-dependent coefficients in the POD subspace are propagated by the recurrent net (closed-loop encoder-decoder updates) and mapped to a high-dimensional state via the mean flow field and POD basis vectors. This model is referred as POD-RNN. The second model, referred to as convolution recurrent autoencoder network (CRAN), employs convolutional neural networks (CNN) as layers of linear kernels with nonlinear activations, to extract low-dimensional features from flow field snapshots. The flattened features are advanced using a recurrent (closed-loop manner) net and up-sampled (transpose convoluted) gradually to high-dimensional snapshots. Two benchmark problems of the flow past a cylinder and flow past a side-by-side cylinder are selected as the test problems to assess the efficacy of these models. For the problem of flow past a single cylinder, the performance of both the models is satisfactory, with CRAN being a bit overkill. However, it completely outperforms the POD-RNN model for a more complicated problem of flow past side-by-side cylinders. Owing to the scalability of CRAN, we briefly introduce an observer-corrector method for the calculation of integrated pressure force coefficients on the fluid-solid boundary on a reference grid. This reference grid, typically a structured and uniform grid, is used to interpolate scattered high-dimensional field data as snapshot images. These input images are convenient in training CRAN. This motivates us to further explore the application of CRAN models for the prediction of fluid flows.

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